Dehradun: It was not just rain. An early geological evaluation held after the devastating flash flood on Tuesday in Dharali village suggests a more complex and violent trigger – a large fall of glacieted sedimentary deposits, possibly due to a regressive slope failure in the mountains.Preliminary estimates made by experts based on satellite data and area analysis indicate an avalanche of approximately 360 million cubic meters of debris. For perspective, a quick, back-of-the-lifhope calculation suggests that the figure is equivalent to more than 1.4 lakh Olympic size swimming pools, which kill the village at a fast pace together. With such an effect, it is not surprising that Dharli had no chance. The avalanche was suddenly raised with a sudden release of malenians and glacio-fluvial materials-under the Kheer silt stream in Dharli. Surge reached the village within seconds, leveling more than 20 structures and claimed the life of at least four people (according to official data).Imran Khan, geologist and head of the Geology Division in Bhutan’s Punatsangchu-e-Hydel Project, who studied satellite imagery of the region, said “it was not a specific cloudburst”. “The incident consisted of a large contingent of probably unconscious glacial deposits, moving at an altitude of 6,700 meters to a height of about 7 km. Heavy rain may have worked as a trigger, but was waiting for a disaster.” Glassel deposits in question, spread over 1.1 sqm with an estimated vertical thickness of 300 meters, located in a hanging trough – a naturally unstable geological characteristic. Narrows in Kheer dad stream, jointly steeply stacked with pre-interlown channels allowed the debris to accelerate the terrible speed, causing almost no time to escape the residents. Khan wrote, “The stream of stream in this region contributes to rapidly raising debris flow to a high longitudinal shield, limited lateral imprisonment, and sharp incision path-” Khan wrote. They added the surface runoff and percolates, after the intense rainy days, could loosen the sediment, which can trigger the collapse.Doon University geologist Rajiv Saran Ahluwalia told TOI that in a velocity of 6-7 meters per second, the flow-filled flows filled with debris are capable of destroying any structure in their way. “And if the velocity doubles, the debris-vaust capacity increases with a factor of 64,” he said. Experts believe that glacial melted, faster than high temperatures in the days before disaster, can complicate volatility. A senior glacieologist stated that the exact reason would only be known to the real -time satellite imagery – captured before and after the event – analyzed or a ground team conducts a survey upstream. “It appears that the flash flood has originated in three narrow valleys, with the most violent bounce in kheer silt. Some extraordinary happened there. This requires immediate investigation.”Geologists have long been called to ban the construction with the steep sewer corridors and the flow paths of the debris, especially in pilgrimage-centered areas such as Gangotry. A geologist involved in the assessment said, “We can no longer ignore the hidden upstream hazards – especially in areas with human and pilgrimage footprints,” said a geologist involved in the evaluation.
